print_levels.cpp

/*
 * BREADTH-FIRST PRINT (LEVEL ORDER TRAVERSAL)
 *
 * This program extends an assumed BinaryTree implementation (from "binary_tree.h") by adding
 * functionality to print the tree in a breadth-first (level order) manner.
 *
 * The algorithm uses a queue to traverse the tree level by level:
 *   - Start from the root node and push it into the queue.
 *   - While the queue is not empty, remove the front node, print its value, and enqueue its children.
 *
 * ASCII Illustration:
 *           10
 *          /  \
 *         5    12
 *             /  \
 *           11    16
 *
 * Example Output:
 * For the tree built by inserting {10, 5, 12, 11, 16}, the printed output will be:
 *   10 5 12 11 16
 *
 * Explanation:
 * The nodes are printed level by level from left to right.
 */

#include "binary_tree.h"
#include <iostream>
#include <queue>

class TreeWithBreadthFirstPrint : public BinaryTree {
public:
    TreeWithBreadthFirstPrint() : BinaryTree() {}

    // Prints the tree in a breadth-first order.
    void print() const {
        if (!root) {
            std::cout << "Tree is empty." << std::endl;
            return;
        }

        std::queue<const Node *> nodesToPrint;
        nodesToPrint.push(root.get());

        while (!nodesToPrint.empty()) {
            const auto *currentNode = nodesToPrint.front();
            nodesToPrint.pop();

            std::cout << currentNode->value << ' ';

            if (currentNode->left) {
                nodesToPrint.push(currentNode->left.get());
            }
            if (currentNode->right) {
                nodesToPrint.push(currentNode->right.get());
            }
        }
        std::cout << std::endl;
    }
};

int main() {
    TreeWithBreadthFirstPrint tree;
    for (const auto &value : {10, 5, 12, 11, 16}) {
        tree.add(value);
    }

    tree.print();

    return 0;
}